Integrated control platform for injection molding system

ABSTRACT

Apparatus and method for controlling an injection molding system having a plurality of devices which generate a corresponding plurality of feedback signals includes structure and steps for providing an operator control station which has a display and at least one operator input device. A single, general-purpose computer is coupled to both the operator control panel and the plurality of injection molding devices and functions to perform multiple-tasking control of both the injection molding functions and the operator control functions. The computer preferably performs real-time closed loop control of the plurality of injection molding devices while also processing system feedback signals and operator input signals. Thus, there is no need for the analog signal processor and the programmable logic controller of the prior art. Preferably, the single general purpose computer has local area network and internet connections to allow external control and feedback of the operating parameters of the injection molding system.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to an integrated control platformfor controlling an injection molding system, and more particularly toapparatus and method for controlling an injection molding system with asingle, general purpose computer which performs both the machine-controlfunctions and the human machine interface (HMI) functions. This controlarchitecture thus obviates the need for the analog signal processor andthe programmable logic controller used in the prior art.

[0003] 2. Description of the Related Art

[0004] Injection molding systems are widely used for producing greatquantities of inexpensive plastic products such as plastic PET preformswhich can be blown into the widely-recognized drink containers. Suchinjection molding systems typically include a plurality of analog anddigital devices which carry out the injection molding operations. Forexample, extruder drives, proportional flow control valves, electricdrives, heating and cooling elements, and other electro-hydro-mechanicaland electromechanical drives are analog devices which perform injectionmolding functions in a well-known way. Examples of digital devicesinclude proximity switches, clamp pressure limit transducers, digitalsolenoid valves, etc. Each of these analog and digital devices must notonly be controlled with appropriate analog and digital commands, butthey are typically provided with feedback sensors which output analogand/or digital feedback signals so that the various devices may beproperly controlled to produce high-volume, quality output from thesystem. For example, the feedback signals may be used in closed loopcontrol to effect real-time changes in the injection molding devices(e.g. temperature set points, injection pressure, etc.). Also, thefeedback signals may be used to display operational information (e.g.status, temperature, parts count, etc.) to the operator at the humanmachine interface or operator control panel.

[0005] In the prior art, it was necessary to utilize an analog signalprocessor (ASP) to provide for real-time control of the various analogdevices in the injection molding system. Likewise, it was necessary toprovide a programmable logic controller (PLC) to control the variousdigital devices in the injection molding system. See, for example, U.S.Pat. No. 5,062,052 (incorporated herein by reference) for an example ofa known injection molding system utilizing both an ASP and a PLC tocontrol the injection molding machine. While the '052 Patent discloses ageneral purpose computer, its use is restricted to interfacing betweenthe PLC and the HMI. Both the PLC and the ASP are still required toperform the injection molding operations.

[0006] The known injection molding control architecture is limited inthat reconfiguration of the injection molding devices cannot be done inreal time. Each of the ASP and PLC must be modified or reprogrammed toeffect the change. Thus, incorporating new technologies in an injectionmolding system often requires that the entire system be shut down forreconfiguration. Additionally, the operational status of each injectionmolding system may only be ascertained at the HMI of each system. Also,injection molding machine manufacturers typically utilize proprietaryarchitecture in their PLC's, thus limiting the variety of new processingtechniques than can be applied to such machines. Furthermore, usingmultiple layers of ASP and PLC processing control imposes a processingpenalty and a bottleneck which reduces the speed at which machinechanges can be accomplished.

[0007] Thus, what is needed is a new injection molding controlarchitecture which provides true real-time control of the injectionmolding system, allows rapid reconfiguration of system devices, permitsthe use of readily available off-the-shelf software, and allows systemstatus and control information to be transmitted beyond the system,e.g., to the factory office or even corporate headquarters.

SUMMARY OF THE INVENTION

[0008] An object of the present invention is to provide an injectionmolding control architecture that enables state-of-the-art hardware andsoftware components to be seamlessly integrated into one controller.Another object is to provide such a control architecture that providestrue real-time controlling and networking capabilities. Yet anotherobject is to provide an open control architecture that allows easyintegration of ancillary equipment and expansion of machine functions.An additional object is to provide intelligent system diagnostics andremote access capabilities to reduce system downtime and toimport/export knowledge and information to/from external sources. Yetanother object is to provide, in one general purpose computer, injectionmolding system control functions, human-machine interface functions,motion control functions, sequence logic functions, continuous processcontrol functions, and communication networking functions.

[0009] Additional objects of the present invention include providing astandard application programming interface, supporting externalcommunications (such as electronic mail, paging, etc., for supervision,trouble-shooting, and information exchange between the system and plantmanagement), providing an expert system with embedded process knowledgeto assist in system and process set up, providing intelligent alarmmanagement and system diagnostics, and providing predefined templateswith embedded options to assist the user in setting up and operating theinjection molding system.

[0010] The above objects and other advantages according to the presentinvention may be achieved by an apparatus for controlling an injectionmolding system which has a plurality of devices that generate aplurality of feedback signals, the apparatus including (i) a humanmachine interface preferably disposed adjacent the injection moldingsystem and having a display and at least one operator input device, and(ii) a general purpose computer coupled to both the human machineinterface and to the plurality of injection molding devices, wherein thegeneral purpose computer performs real-time closed loop control of theplurality of injection molding devices based on the plurality of commandand feedback signals.

[0011] According to another aspect of the present invention, a singlecomputer for controlling an injection molding system having a pluralityof injection molding devices which carry out injection molding processesand provide feedback signals, and a human machine interface having adisplay and at least one manual input device for inputting operatorcommands, includes (i) a first input/output for receiving commandsignals from the human machine interface manual input device or devices,and for providing display signals to the human machine interfacedisplay, (ii) a second input/output for receiving the feedback signalsdirectly from the plurality of injection molding devices, and forproviding real-time control signals directly to the plurality ofinjection molding devices, and (iii) a CPU for generating the real-timecontrol signals in accordance with the feedback signals and the commandsignals, the CPU performing multi-tasking processing of the commandsignals, the display signals, the feedback signals, and the controlsignals.

[0012] Another aspect of the present invention features an injectionmolding system which comprises (i) a plurality of injection moldingdevices for performing injection molding operations, the plurality ofdevices receiving real-time control signals and outputting real-timefeedback signals, (ii) a human machine interface having a display and atleast one operator input device, and (iii) a single processor whichreceives the real-time feedback signals from the plurality of injectionmolding devices and command signals from the operator input device,multi-task processes the received signals in accordance with a pluralityof predetermined injection-molding control programs and displayprograms, outputs the real-time control signals to the plurality ofinjection molding devices and outputs the display signals to the humanmachine interface display in accordance with the plurality ofpredetermined injection-molding control programs and display programs,and has an operating system which is capable of running commercialsoftware.

[0013] In accordance with another aspect of the present invention, amethod of controlling an injection molding machine which has a pluralityof injection molding devices that perform injection molding processesand provide feedback signals, and a human machine interface with adisplay and at least one operator input device, includes the steps of(i) inputting to a single processor the feedback signals and signalsfrom the operator input device or devices, and (ii) using the singleprocessor to control, in real-time, both the plurality of injectionmolding devices and the control panel display.

[0014] A further aspect of the present invention features at least onecomputer-readable storage medium for storing computer-readable datawhich causes a single general purpose computer to control an injectionmolding system which has a plurality of injection-molding devices thatperform injection molding operations and produce a plurality of feedbacksignals, and a human machine interface having a display and at least oneoperator input device, the computer-readable storage medium causing thesingle general purpose computer to (i) receive the feedback signals andsignals from the human machine interface operator input device ordevices, and (ii) perform multi-task processing to control both theplurality of injection molding devices and the human machine interfacein real-time, the multi-tasking processing performing human machineinterface functions with lower priority in the “background” andinjection molding device functions with higher priority in the“foreground”.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The present invention is described in conjunction with theaccompanying drawings in which:

[0016]FIG. 1 is a schematic block diagram of an injection molding systemin accordance with the present invention;

[0017]FIG. 2 is a schematic block diagram of both the human machineinterface and the general purpose computer according to the presentinvention;

[0018]FIG. 3 is a schematic diagram of the software control module inaccordance with the present invention; and

[0019]FIG. 4 is a schematic view of the control architecture accordingto the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] 1. Introduction

[0021] The advantageous features of the present invention will bedescribed with respect to the plastic injection molding system ormachine to be described below. However, the invention is not limited tosuch embodiments, but may be applied to any injection molding technologywithin the scope of the attached claims.

[0022] The control architecture according to the present inventionprovides both real-time control of the injection molding system andreal-time interface with the operator controls. The architecture alsoincludes the human machine interface (HMI) required for the operationand monitoring of the injection molding system, as well as an interfaceto the factory and corporate headquarters for information exchange.Software and hardware are integrated to convert a general purposecomputer into a system controller which not only controls the machinefunctions and the operator controls, but has an open architecture toenable easy integration of any ancillary equipment and informationexchange with external systems and networks. In addition, the generalpurpose computer is extended, by additional hardware and software, toprovide deterministic real-time control of an injection molding systemto achieve high performance and intelligent manufacturing cells.

[0023] Thus, the flexible and reconfigurable manufacturing systemaccording to the present invention can easily adapt new technologies andprocesses, extending critical, real-time performance data beyond thehuman machine interface on the factory floor to other plant departmentsand corporate headquarters to provide real-time information to allbranches of the organization. The use of commercial, general purposecomputer (PC) technologies allows the use of better and faster CPU's,more robust operating systems, many different peripherals, a wide rangeof communications and network capabilities, and the ability to extendthe control of the machine from the factory floor to a remote site.

[0024] 2. The Injection Molding System Control Architecture

[0025]FIG. 1 is a schematic block diagram showing the general featuresof the injection molding system control architecture according to thepresent invention. In FIG. 1, an injection molding system or machine 10carries out injection molding processes utilizing digital devices 12,14, 16, and 18, and analog devices 20 and 22, in a well-known manner.Each of the digital and analog devices preferably includes an input fordriver control and an output which provides feedback signals used inclosed Loop control of the device. Digital devices 12, 14, and analogdevices 20, 22 preferably receive control signals from, and outputfeedback signals to, field bus 24 (to be described below); while thedigital devices 16 and 18 receive control signals from, and outputfeedback signals to, digital bus 26 (to be described below). Of course,depending on the particular injection molding system being controlled,either the field bus 24 or the digital bus 26 may carry all necessarycontrol and feedback signals to control the injection molding process.

[0026] A human machine interface (or control panel or station) 30 isused by the operator to input control data and to view process feedbackinformation. The HMI 30 has a keyboard 32 and a pointing device (such asa mouse) 34 which are used by the operator to input data. A systemfunction keypad (which may include an LED display) device 36 may also beused by the operator to input specific machine commands, depending uponthe system to be controlled. A display 38 provides the operator with atleast one viewing device for observing a display based on feedbacksignals, and provides an interface for manually-input data. A removablestorage device drive 40 (such as a floppy disk drive) may also belocated at the control panel 30 for the operator to input programmedcontrol information, new control programs, or to download feedback datato a removable storage device. The control panel 30 also includes amultiplexer 42 (to be described below) which multiplexes the variouscontrol and feedback data between the HMI 30 and the general purposecomputer 44.

[0027] The general purpose computer 44 is preferably an off-the-shelfpersonal computer having a CPU 46, a ROM 48, and a RAM 50. Preferably,the computer 44 includes a control panel interface 52 which is coupledto the multiplexer 42 of the HMI 30 through a bi-directional, greaterthan 1 Gigabit per second serial bus link 54 (to be described below).The interface 52 is preferably a Beckhoff Industrial Electronics CP-LinkPC Multiplexer. While not shown, the general purpose computer 44 may beequipped with such peripherals as a CRT, a keyboard, a disk drive, aCD-ROM drive, a mouse, a touch screen, a light pen, etc.

[0028] The computer 44 also has a digital interface 56 which is coupledto the digital bus 26 through a connection 58. Likewise, the computer 44has an interface 60 which is coupled to the field bus 24 through aconnection 62.

[0029] The computer 44 also includes a local area network interface 64which may be coupled to a local area network (e.g., Ethernet; not shown)used within the factory. Also, the computer 44 may include a modem orother external interface 66 which may be used to connect the computer 44to, e.g., the internet or an intranet.

[0030] With the structure described above, the control architectureaccording to the present invention can conduct true real-time, closedloop control of the injection molding devices 12-22 without the need ofa PLC or an ASP, as were required in the prior art. Additionally, theoperator can control the injection molding process from the HMI 30through the computer 44. The computer 44 has sufficient processing speedand power to multi-task process both the injection-molding functions andthe HMI functions. For example, the computer 44 may process instructionsfor the high-priority closed-loop controlled injection molding devicesin foreground, while processing instructions for the lower-priority HMIfunctions in background. Thus, the computer 44 will interleaveprocessing of machine control functions and HMI functions.

[0031] 3. The General Purpose Computer

[0032] As noted above, the single, general purpose computer according tothe present invention includes a hardware architectures similar to thatof a standard, general purpose commercial or industrialized personalcomputer, and preferably operates under a general-purpose operatingsystem such as Windows NT (Tm). Preferably, the computer 44 is a ModelC6150 Industrial PC from Beckhoff Industrial Electronics. This PCfeatures a Pentium II microprocessor with a 2.0 Gigabyte (or higher)hard drive, and a 64K RAM memory. The computer may also be equipped witha CD ROM drive, 1.44K and/or 120 MB disk drives, four serial interfaces,a printer interface, and several (e.g. seven) slots for additionalcards. Interfaces for local area networks and/or internet/intranetconnectivity are preferably installed in the extra slots. The computeris capable of simultaneously multi-tasking at least three functions,i.e., control of the injection molding system, control of the HMI, andserving as a plant-wide network server.

[0033] The computer 44 performs A/D and D/A functions in order toreceive the analog feedback signals and provide analog control signalsthrough the field bus 24. Thus, the computer 44 processes all controlprograms, HMI programs, and network programs in the digital regime. Byoperating in the digital regime, the computer 44 provides betterperformance and more accurate solutions than traditionally offered byanalog circuitry. The high computation power and generous working memorysize of the computer 44, together with a software real-time extensionkernel (to be described below) provides real-time performance formachine control, HMI functions, and network functions. Since thereal-time extension kernel operates on microsecond resolution, thecomputer 44 operates as a multi-tasking scheduler for all computerfunctions. That is, the computer 44 may simultaneously control all ofthe injection molding devices using multi-tasking processing.Additionally, such machine control functions can be multi-taskedtogether with the HMI functions and/or the network functions. The systemis capable of achieving injection molding device control loop updates onthe order of milliseconds, which renders the use of an analog closedloop controller for real-time control of the injection molding devicesunnecessary.

[0034] Thus, the computer 44 can control the injection molding devicesusing a plurality of predetermined device-control programs, (e.g., resininjection, mold clamp operation, etc.), and also controls the HMI 30utilizing a plurality of predetermined HMI programs (e.g., display,keyboard, mouse, keypad, etc.). The computer 44 also networks with othercomputing devices through a local area network (and/or the internet)utilizing a plurality of predetermined programs such as internetbrowsers, word processing programs, spreadsheet programs, etc. Not onlydoes the computer 44 operate a plurality of such control and networkingprograms, it can do so in real-time by multi-tasking the processing inaccordance with a predetermined priority, such as critical injectionmolding devices first, feedback and status devices second, MHI devicesthird, and network communication functions last. Moreover, the openarchitecture of the computer 44 allows any of these predeterminedcontrol and networking programs to be modified, upgraded, installed, orchanged, as required.

[0035] Not only does the computer 44 obviate the need for an ASP, italso replaces the PLC used at the prior art. The ability to easilyinstall new application program software into the computer 44 provides amethod of mapping process inputs/outputs to process images which can bedisplayed to the operator. The computer 44 is enabled with input andoutput capabilities as well as a -real-time kernel extension to itsgeneral-purpose operating system and programming software, in accordancewith an international industrial standard such as IEC 1131-3. Thus, thecomputer 44 replaces the commonly used PLC or proprietary controllerswhich control the operating sequences of various injection moldingsystem devices to perform the required injection molding functions. Inaddition to acting as the master for controlling the machine functions,the computer 44 also acts as an information archive which concentratesall operational information of the machine devices and machine statuswhich may then be transmitted to a factory supervisory system.

[0036] 4. Real-Time Extension Kernel

[0037] As noted above, the computer 44 according to the presentinvention preferably runs a real-time extension kernel to the operatingsystem such as Windows NT. This kernel permits more rapid multi-taskingprocessing of the machine functions, HMI functions, and networkfunctions. Several commercial automation solution software packages areavailable which provide real-time processing for a general purposecomputer. These real-time extension kernels allow for processingindependence yet use the power development of a general purposecomputer. The preferred embodiment uses the TwinCAT Real-time KernelExtension developed by Beckhoff Industrial Electronics. The TwinCATkernel extension offers a base for PLC and motion control solutions. TheTwinCAT kernel is a run time system with real-time execution ofprograms, tools for programming, analysis tools, and configurationmanagement functions. Fill Windows programs (e.g., visualization andOffices products) may interact with TwinCAT via standard Microsoftinterfaces to exchange data and control servers. Thus, the real-timekernel extension according to the present invention allows formulti-tasking processing, is completely integrated into the operatingsystem, allows all standard features of the Windows NT Operating Systemto remain unchanged, allows the CPU capacity to be shared betweencontrol real-time tasks and NT by the user, and provides pure softwaresolutions without further need for hardware.

[0038] 5. Human Machine Interface

[0039] The HMI (or control panel or station) 30 is used to input controlinformation to control the injection molding devices 12-22, and toreceive feedback from those devices for display, storage, ortransmission. The HMI 30 includes such standard control equipment as thekeyboard 32, the pointing device (mouse) 34, the keypad 36, theremovable storage device 40, the display 38, and the multiplexer 42.Preferably, the HMI 30 is a Beckhoff CP7000 series control panel havingspecial PLC keys with LED displays, a touch screen, a 15 inch TFTdisplay, a PC keyboard, a 3 and ½ inch disk drive, and a CP-Linkinterface.

[0040] In the present invention, the effectiveness of the communicationbetween the HMI 30 and the computer 44 is greatly improved due to theintegration of the operator interface and machine control functions intoa single general purpose computer which eliminates the processingbottleneck normally imposed by the communication links between the HMI,the PLC, and the ASP, as used in the prior art.

[0041] Referring to FIG. 2, the HMI 30 is shown connected to thecomputer 44 through the greater than 1 Gigabit serial bus link 54. Theuse of such a high speed bi-directional multiplexed bus between the HMI30 and the computer 44 allows the physical separation of the operatorcontrol and the display elements from the computer 44. In the preferredembodiment, the link 54 is as long as 50 meters, although lesser lengthssuch as 10 meters may be appropriate. By housing the computer 44 awayfrom the HMI 30, all delicate computer devices such as hard disk drives,modems, the CPU, etc. can be protected from the heat, vibrations, andimpacts normally encountered in an injection molding environment. Thishigh-speed link enables the HMI 30 to be installed near the machine 10and at an optimum location for ease of operation while maintaining asufficient separation from the computer 44. For this reason, theelectronics residing inside the HMI should be the minimum required todisplay data, allow data input, and facilitate manual command functionsthrough the keyboard 32, the pointing device 34, and the function keypad36.

[0042] In FIG. 2, the display at the HMI is preferably a TFT display382, although the display may be an LED, an LCD, a CRT, or otherequivalent display devices. The HMI 30 also includes one or morepointing devices 342 which may comprise a mouse, light pens, a touchscreen devices, etc. The keyboard 32 is, preferably, a standard PCkeyboard, although specialized keyboards with specialized function keysmay be used. The machine function keys and LED display 36 are thosetypically found in known injection molding systems. The removablestorage device 40 is used to input control program or setpointinformation, or to store feedback signals. The above-discussed input andoutput devices are connected to the HMI multiplexer 42 which multiplexesthe information for transmission over the greater than 1 Gigabit serialbus link 54. The multiplexer 42 also controls a 5 volt power supply (notshown). Lastly, the HMI 30 may include an emergency stop button ordevice 80 which may be used to stop the injection molding devices in anemergency. The emergency stop button 80 is connected to safety circuits82 which, in turn, are connected to the computer 44 through an interface(not shown).

[0043] The link 54 provides bi-directional communication between the HMIand the computer 44, and this greatly simplifies the architecture andimproves the reliability of the system. The bi-directional link 54connects the HMI 30 to the computer 44 for video control and data input.The computer 44 thus processes the bulk of HMI information instead ofthe HMI 30. The speed of communication between the HMI 30 and thecomputer 40 is in the Gigabit/s range, and this allows the computer 44to provide real-time response from operator-initiated changes to themachine devices 12-22. The link 54 can be implemented bycommercially-available links such as PanelLink, products based on aninternational industrial standard such as IEEE P1349b, or CP-Link fromBeckhoff Industrial Electronics, or equivalents. In the preferredembodiment, the CP-Link from Beckhoff is used.

[0044] The HMI 30 thus has minimum processing capability, preferablyonly those required to display data, allow data input, facilitatemanually-controlled functions through the function keys 36, and tocommunicate with the operator through graphic, text, and video display.Since the computer 44 can be housed away from the HMI 30 (e.g., in acontrol cabinet) in a controlled environment to protect the delicatecomputer devices, the operator control and display functions can bemoved closer to the injection molding system for closer observation ofmachine functions by the operator.

[0045] The bi-directional link 54 may comprise a two wire coaxial cable,two single wire coaxial cables, one or more fiber optic cables, or othercommunication means. No additional power supply is usually needed forthe link 54. The cable interface may comprise a printed circuit boardconnected to a standard personal computer bus (e.g., ISA, or PCI), andtherefore may be used with any general purpose computer.

[0046] As shown in FIG. 2, the computer 44 may include additionalstructure to that depicted in FIG. 1. In particular, the computer 44preferably also includes an LCD graphics controller board 84 forcontrolling the display 382. Preferably, the controller 84 includes anLCD interface. The computer 44 also includes a keyboard interface 86 forkeyboard 32, and a removable storage device controller 90, whichcontrols the removable storage device 40. The serial interface 88 isused to control the serial communication ports.

[0047] Signals from the computer interfaces for the LCD, the keyboard,the pointing devices, the communication ports, and the removable storagedevices are converted by the PC interface link board 52 to a highfrequency serial signal which is then transferred to the HMI 30 throughthe link 54. The HMI multiplexer 42 converts the serial signal back tothe original computer interface-generated signals, which are thentransmitted to the various devices for control and feedback. Thus, thedevices on the HMI 30 may be controlled from the computer 44 over muchlonger distances than would normally be possible. Since the link 54preferably has at least two separate channels, there is a link channelfor each communication direction between the control panel 30 and thecomputer 44.

[0048] The computer 44 also includes an interface 56 for interfacingdirectly, when required, to digital devices 16 and 18 over the digitalbus 26, as seen in FIG. 1. Preferably, the interface 56 is a SERCOS(Serial Real-time Communication System). Again, the open architecture ofthe computer 44 allows control of injection molding devices 16 and 18directly through the digital bus 26 or, alternatively, through thefieldbus 24.

[0049] 6. Fieldbus

[0050] In FIG. 1, the computer 44 interfaces with digital injectingmolding devices 12, 14, and analog injection molding devices 20, 22through the fieldbus 24. Preferably, the fieldbus 24 is a standardindustrial fieldbus, such as a CANopen bus, a Lightbus, an Interbus, aControlNet bus, a Profibus DP/FMS, or an equivalent device. The ProfibusDP operating at 12 MBit/s is used in the preferred embodiment. As notedabove, the computer 44 may also use a digital bus 26 (preferably SERCOS)to interface to digital servo drives and other digital devices 16, 18.

[0051] The integration of inputs from the injection molding devices,sensors, and control outputs for actuators and digital drives isachieved by an open device network interface of the computer 44. Thecontrol platform of the computer 44 supports all major devicefieldbuses. The use of an industrial-grade fieldbus with a high-speedmultiplexed signal bus, operating under fault tolerant protocol,replaces the multiple dedicated wires used in the prior art. Thiseliminates the cost and reliability problems associated with dedicatedwiring. The interface protocol of the fieldbus is preferably implementedusing microcontrollers. Such microcontrollers can directly take care ofunwanted effects such as signal noise, and can also perform afeasibility check of the commands. Additionally, integrating a fieldbusinterface with a dedicated controller provides so-called “controlislands”. Control islands comprise dedicated inputs/outputs andlocalized processing capabilities to achieve a distributed controlarchitecture that pushes the controller closer to the system beingcontrolled by moving intelligence and responsibility closer to thenetwork edge. The ability to solve problems locally reduces the trafficburden on the network backbone (i.e., the CPU in the computer 44). Asinjection system functions can be partitioned into application specificsub-systems with well-defined and clustered control elements, the use ofcontrol islands to provide the control of the sub-system greatlyenhances the modularity and performance of the control system. Thecontrol islands are connected to the system controller through physicalfieldbus connections. These connections provide logical connection,messages; both loosely coupled to provide scalability of the controlsystem.

[0052] 7. Control Software

[0053]FIG. 3 is a view of the preferred control software moduleaccording to the present invention. FIG. 3 is in the form of afunctional block diagram of the software control architecture used inthe computer 44. In FIG. 3, the control software 300 includes a softwaremodule for sequential control 302, a software module for data logging304, and a software module for alarm management 306 (to be describedbelow). Interfacing with the above-three software modules are aninitialization and process control module 308, an operation mode module310, a synchronization and coordination control module 312, and an inputsignals processing module 314. The initialization and process controlmodule 308 sends control signals 316 to the injection molding system 10,while sensor signals 318 from the injection molding system 10 areprovided to the input signals processing module 314. The module 314 alsoreceives sensor signals from other software control modules (not shown).

[0054] Operator inputs 320 from the HMI 30 are provided to the operationmode module 310, which provides inputs to the modules 302, 304, and 306.Other HMI interface signals 322 are provided to the synchronization andcoordination control module 312, which also interfaces with the modules302, 304, and 306. This software control architecture provides greatflexibility for upgrading and/or modifying the existing software.

[0055]FIG. 4 is a functional block diagram of the control architectureaccording to the present invention. In FIG. 4, the injection moldingprocess 400 utilizes the injection molding system 10 to performinjection molding operations. The injection system elements 402 comprisethe devices 12-22 which are driven by digital and analog outputs 404received over the fieldbus 24. The feedback sensors 406 associated withthe machine elements 402 provide digital and analog feedback signalsthrough the fieldbus 24.

[0056] Position measurement device or devices 408 provides measurementof the actual position of the process and is driven by a servomotor 410which receives controlled power from digital drive controller 412.Inputs and outputs 414 are coupled with the position measurement deviceor devices 408 and the information is transmitted to the digital drivecontroller 412 which transmits signals to/from the computer 44 over thedigital bus 26.

[0057] The computer 44 communicates digital and analog signals over thefieldbus 24 through a fieldbus master 420. Likewise, the computer 44communicates digital signals over the digital drive 26 through a digitalbus drive master 422. Signals communicated to/from the HMI 30 aretransmitted over the link 54 through the interface 52, such as a PCmultiplexer. The computer 44 includes software-based programs whichcarry out functions for: inputs and outputs mapping 424; temperaturecontrol 426; programmable logic control 428; hydro-mechanical motioncontrol 430; electromechanical motion control 432; and process control434. Furthermore, the computer 44 may include other software-basedfunctions such as engineering and business software tools 436 and HMIapplication software 438.

[0058] The control software, control programs, HMI programs, and othersoftware may be loaded into the computer 44 from computer-readablestorage medium or media such as disks, CD ROM's, tapes, magnetic-opticaldisks, etc., or remotely through the LAN or internet connections.

[0059] The control architecture depicted in FIG. 4 integrates real-timecommands, programmed commands, and manual commands. Since it features ageneral purpose computer with an open architecture, modifications andupgrades to all of these commands can be conveniently input. Thereal-time kernel running in the general purpose operating systemprovides real-time injection molding system control interlaced withprogrammed and manual inputs in multi-tasking processing. The real-timekernel provides high priority for the system control and a window forprocessing the general purpose information.

[0060] The control architecture includes multiple levels which processunder the multi-tasking scheduler of the kernel, with each level itselfperforming its specific functions. The real-time closed loop systemcontrol and the real-time high speed switching in response to systemelement feedback signals are executed at the highest priority, alongwith emergency stop and ordered shutdown functions. Software providesthe function of a programmable logic controller to control the systemoperations sequence. The same computer, in the background level,performs the HMI functions, although the speed of communications and theprocessing power of the computer will allow the HMI functions to beperformed virtually in real time. A common database is shared betweenthe machine control functions and the HMI functions to improve thethroughput of the information processing by eliminating themultiple-processor bottleneck imposed by the prior art.

[0061] The general purpose computer is capable of interfacing with awide variety of peripheral devices such as a CD ROM, a modem forintranet/internet or remote connectivity, and a local area network suchas Ethernet for plant-wide communications. Thus, a single computerperforms the functions of closed-loop control of the injection moldingsystem, sending commands and status either locally via the installedsystem devices or remotely via communication means to/from other sites,receiving input data from the HMI or from network-connected clients, andcontrolling displays at the HMI.

[0062] 8. Additional Capabilities

[0063] Since the general purpose computer has a great deal of processingpower, it can also provide additional capabilities useful in aninjection molding environment. For example, the general purpose computercan perform smart filtering of information, provide an expert system toimprove the process set-up and operation, and provide an alarmmanagement system.

[0064] Smart filtering is a processing technique to selectively filtersignals processed by the CPU to limit information overload at thehigh-priority multi-tasking processing levels. It is the process ofselecting levels of information for further processing of data.Non-critical data is excluded from the system as the level of networkmanagement rises, so that the top network management consoles canconcentrate on higher-level concerns like trend analysis and capacityplanning. This also reduces the burden on the network and improves thecommunication throughput in the entire network. The general purposecomputer of the present invention can include such smart filteringprocessing so that predetermined system-level signals need not betransmitted through the network.

[0065] The high processing power of the single general purpose computeraccording to the present invention enables it to be used in an expertsystem to manage the injection molding system. Such an expert systemadds value to the alarm management system (to be discussed below) bydiagnosing process disruptions, generating more precise operatorinformation, and assisting in implementation of corrective actions (suchas reconfiguring the system “on the fly”). This results in a more robustalarm management system to help operators manage process disruptionssafely and efficiently, and minimize system down time. The expert systemcan also add value to process set-up by providing the operator with therecommended process parameters based on knowledge specific to thatsystem stored in the computer memory. The computer can also archivematerial information for its associated mold, or it can store thisinformation in a remote location through the intranet/internet access.

[0066] Expert systems are applications of artificial intelligence thatapply an inference engine, fuzzy logic technologies and/or other methodsto reason, in real-time, about events that occur in dynamic processessuch as those used in injection molding. The inference engine reasonsabout specific predetermined rules defined in a knowledge base that isderived from empirical data and operator input.

[0067] The use of the general purpose computer in a real-time expertsystem in accordance with the present invention can be used in at leasttwo ways, as an advisory system and as a supervisory control system. Inadvisory applications, the expert system reasons about dynamic changesin process data, makes decisions based on process events, and presentsconclusions and a rationale to the operator. The expert system thusprovides timely and accurate advice to the operator concerning processoccurrences and impending problems. In the supervisory controlapplications, the expert system according to the present inventionpro-actively assists operators by adjusting set points and switchingdiscrete equipment on or off to resolve problems, optimize moldingoperations, or achieve other objectives defined in the knowledge base,such as predictive maintenance. It is the high processing power of thegeneral purpose computer according to the present invention whichprovides the opportunity to realize an expert system in an injectionmolding environment.

[0068] Many injection molding systems have an alarm system that alertsthe operator of system malfunctions and may also execute a systemfunction set such a stepped shutdown, slowdown, etc. The single generalpurpose computer according to the present invention has enoughprocessing power to allow the computer to manage an intelligent alarmsystem, i.e., an alarm system that reasons about the state of alarms.This allows the computer or the user to apply a higher level of logic tothe system functions so that the system is not simply shut down with thesubsequent impacts on system performance and productivity. That is, thecomputer may continue to operate the injection molding system, but at alower rate, if alarm analysis indicates only minor difficulties such asa slightly higher temperature.

[0069] The intelligent alarm system according to the present inventioncan thus accurately capture the dynamic changes occurring in theinjection molding system during different alarm conditions. For example,the system can be automatically controlled to stop or merely produce ata lower rate; or the operator can be prompted to input additional datato correct the condition which generated the alarm. Moreover, ifadditional information on an alarm condition is required by thecomputer, the operator can input such data at the HMI based on thefeedback information presented on the display. The operator can alsoconsult an on-line operating manual (stored in the computer memory) toprovide timely corrective information for the alarm condition. Suchalarm management information can be made available to the operator intext, graphic, audio, and even video forms.

[0070] The intelligent alarm management system according to the presentinvention can provide predetermined actions for any conditions such asalarm activation, alarm acknowledgement, and alarm cessation. Actionsmay range from a simple advisory text message, to paging an operator inthe factory, or sending electronic mail to the maintenance department,the plant supervisor, or other engineering personnel through a network.

[0071] Since the computer according to the present invention may includea general-purpose operating system, the real-time or stored feedbacksignals can be used in off-the-shelf business applications software,such as spreadsheets or relational database management. Thus,statistical process analysis and preventive or predictive maintenancefunctions may be accomplished by the computer of the present invention,or by another server coupled to the computer through the network. Also,since the computer of the present invention preferably adopts the opendata communications standards known in the computer industry, this willeliminate the need for propriety drivers presently used in the injectionmolding industry. Even if certain manufacturers require proprietarydrivers for certain injection molding devices, these drivers can berapidly downloaded to the computer 44 through the internet and the modem66.

[0072] Preferably, the computer according to the present inventionincludes a plurality of predetermined set-up programs (wizards) whichwalk the operator through set-up in an easy-to-understand fashion. Forexample, a series of pre-defined templates may be presented to theoperator which allows options for selection in data fields for the inputof the desired parameters for the particular system. Such wizards may beprovided for each individual system or for an entire class of systemsand may be upgraded through the internet or local network connection.

[0073] 9. Conclusion

[0074] Thus, what has been described is a single, general-purposecomputer for an injection molding system which eliminates the need for aprogrammable logic controller or an analog signal processor, multi-taskprocesses the injection molding functions and the HMI functions, andprovides open communications with a local area network and/or theinternet. This is a powerful tool in improving the accuracy andproductivity of the injection molding system itself, and also improvingmanagement access and control of the system operations.

[0075] Of course, other embodiments of the present invention may beconceived by those of skill in the art. For example, the general purposecomputer of the present invention may control more than one injectionmolding system, or it may control an injection molding system and one ormore ancillary machines such as a conveyor belt, a robot, or otherproduct-handling equipment. The control of such machines may beintegrated in the single processor of the present invention to provide asmooth flow of products through the factory.

[0076] Additionally, the HMI for each system does not have to be locatedimmediately adjacent to that system. For example, a central controlstation may be provided with a plurality of control panels from aplurality of systems so that one operator can control a number ofinjection molding and ancillary machines. In this configuration, thegeneral purpose computer may be located at the operator control station,or at a remote location. Extending this configuration, it can be seenthat the computer 44 (or even the HMI's) may be located in the factoryoffice so that management receives immediate operational information andcan rapidly reconfigure injection molding operations.

What is claimed is:
 1. Apparatus for controlling an injection moldingsystem having a plurality of devices which generate a correspondingplurality of feedback signals, said apparatus comprising: a humanmachine interface having a display and at least one operator inputdevice; and a general purpose computer coupled to both said humanmachine interface and to the plurality of injection molding devices,said general purpose computer performing real-time closed loop controlof said plurality of injection molding devices based on the plurality offeedback signals.
 2. Apparatus according to claim 1, wherein saidgeneral purpose computer performs real-time closed loop control of saidplurality of injection molding devices based on data received from theoperator input device.
 3. Apparatus according to claim 1, wherein saidgeneral purpose computer performs multi-tasking processing of the closedloop control of said plurality of injection molding devices. 4.Apparatus according to claim 1, wherein said general purpose computerperforms multi-tasking processing of (i) the closed loop control of saidplurality of injection molding devices and (ii) data received from theoperator input device or devices.
 5. Apparatus according to claim 1,wherein said general purpose computer has an open architecture forrunning off-the-shelf software unrelated to the control of the injectionmolding machine.
 6. Apparatus according to claim 1, wherein said generalpurpose computer has an interface for coupling said general purposecomputer to at least one of a local area network and the internet. 7.Apparatus according to claim 1, wherein said general purpose computerperforms the real-time closed loop control of said plurality ofinjection molding devices in the absence of an analog signal processorand a programmable logic controller.
 8. Apparatus according to claim 1,wherein said general purpose computer is disposed remote from saidoperator control panel.
 9. Apparatus according to claim 1, furthercomprising: a field bus connecting said general purpose computer to saidplurality of injection molding devices; and a serial bus link connectingsaid general purpose computer to said operator control panel. 10.Apparatus according to claim 9, wherein said field bus comprises ahigh-speed multiplexed signal bus which carries said plurality offeedback signal to said general purpose computer, and carries real-timecontrol signals from said general purpose computer to said plurality ofinjection molding devices.
 11. Apparatus according to claim 9, whereinsaid serial bus comprises a bi-directional, gigabit serial bus capableof carrying multiplexed data between said general purpose computer andsaid operator control panel.
 12. Apparatus according to claim 11,wherein said serial bus is more than about 10 meters long and operatesat above about one gigabit per second.
 13. Apparatus according to claim1, wherein said general purpose computer performs smart filtering ofsaid feedback signals, and performs alarm management based on thefiltered feedback signals.
 14. A single computer for controlling aninjection molding system having (i) a plurality of injection moldingdevices which carry out injection molding processes and provide feedbacksignals, and (ii) a human machine interface having a display and atleast one manual input device for inputting operator commands, saidsingle computer comprising: a first input/output for receiving commandsignals from said human machine interface manual input device, and forproviding display signals to the human machine interface display; asecond input/output for receiving the feedback signals directly from theplurality of injection molding devices, and for providing real-timecontrol signals directly to the plurality of injection molding devices;and a CPU for generating the real-time control signals in accordancewith said feedback signals and said command signals, said CPU performingmulti-tasking processing of said command signals, said display signals,said feedback signals, and said control signals.
 15. A computeraccording to claim 14, wherein said CPU performs said multi-taskingprocessing according to a predetermined priority of tasks.
 16. Acomputer according to claim 15, wherein said CPU runs an off-the-shelf,real-time extension kernel to perform said multi-tasking processing. 17.A computer according to claim 14, wherein said CPU controls theplurality of injection molding devices in the absence of an analogsignal processor.
 18. A computer according to claim 14, wherein said CPUperforms real-time closed loop control of the plurality of injectionmolding devices based on said feedback signals.
 19. A computer accordingto claim 14, further comprising a third input/output for transferringinjection molding signals to/from at least one of a local area networkand the internet.
 20. A computer according to claim 14, wherein said CPUhas an open architecture capable of running off-the-shelf softwareunrelated to control of said plurality of injection molding devices. 21.An injection molding system comprising: a plurality of injection moldingdevices for performing an injection molding operation, said plurality ofinjection molding devices receiving real-time control signals andoutputting real-time feedback signals: a human machine interface havinga display and at least one operator input device; and a single processorwhich (i) receives the real-time feedback signals from said plurality ofinjection molding devices and command signals from said at least oneoperator input device; (ii) multi-task processes the received signals inaccordance with a plurality of predetermined injection molding controlprograms and display programs, (iii) outputs the real-time controlsignals to the plurality of injection molding devices and outputsdisplay signals to the human machine interface display in accordancewith the plurality of predetermined injection-molding control programsand display programs, and (iv) has an operating system which is capableof running commercial software.
 22. A system according to claim 21,wherein said single processor has a Windows NT operating system andmulti-task processes using an off-the-shelf real-time extension kernel.23. A system according to claim 21, wherein said plurality of injectionmolding devices includes an analog device and a digital device, andwherein said single processor controls both said analog device and saidsignal device.
 24. A system according to claim 21, wherein saidprocessor is disposed remote from said control panel and said pluralityof injection molding devices.
 25. A system according to claim 21,wherein said single processor has an interface fortransmitting/receiving signals to/from a remote processor.
 26. A systemaccording to claim 21, wherein said single processor performs real-timecontrol of said plurality of injection molding devices and real-timecontrol of said control panel display.
 27. A method of controlling aninjection molding system which has (i) a plurality of injection moldingdevices that perform injection molding processes and provide feedbacksignals, and (ii) a human machine interface with a display and at leastone operator input device, comprising the steps of: inputting to asingle processor the feedback signals and signals from the operatorinput device; and using said single processor to control, in real-time,both said plurality of injection molding devices and said human machineinterface display.
 28. A method according to claim 27, wherein saidsingle processor performs multi-tasking processing of said feedbacksignals and signals from the operator input device.
 29. A methodaccording to claim 28, wherein said single processor has an openarchitecture capable of running commercial software.
 30. A methodaccording to claim 29, wherein said single processor performsmulti-tasking processing using a real-time extension kernel.
 31. Amethod according to claim 27, wherein said single processor controlsboth said plurality of injection molding devices and said control paneldisplay in the absence of a programmable logic controller and an analogsignal processor.
 32. A method according to claim 27, wherein saidsingle processor is disposed remote from said injection molding machine.33. A method according to claim 32, wherein said single processorcommunicates with said control panel by multiplexing information over agigabit serial bus.
 34. A method according to claim 33, wherein saidsingle processor communicates with said plurality of injection moldingdevices over a field bus having an error correction function.
 35. Amethod according to claim 27, wherein said single processor performsclosed loop control of said plurality of injection molding devices. 36.At least one storage medium for storing computer-readable data whichcauses a single general purpose computer to control (i) an injectionmolding system having a plurality of injection molding devices thatperform injection molding operations and produce a plurality of feedbacksignals, and (ii) a human machine interface having a display and anoperator input device, said computer-readable data causing the singlegeneral purpose computer to: receive the feedback signals and signalsfrom the human machine interface operator input device; and performmulti-task processing to control both the plurality of injection moldingdevices and the human machine interface in real-time, said multi-taskingprocessing performing human machine interface functions in backgroundand injection molding device functions in foreground.
 37. At least onestorage medium according to claim 36, wherein said computer-readabledata causes the single general purpose computer to perform closed loopcontrol of said plurality of injection molding devices in the absence ofa programmable logic controller and an analog signal processor.
 38. Atleast one storage medium according to claim 36, wherein saidcomputer-readable data causes the single general purpose computer toperform said multitasking processing using a commercial real-timeextension kernel having a multi-tasking scheduler.
 39. At least onestorage medium according to claim 36, wherein said computer-readabledata causes the single general purpose computer to perform errorcorrection control of said feedback signals and the signals from thecontrol panel operator input device.
 40. At least one storage mediumaccording to claim 36, wherein said computer-readable data causes thesingle general purpose computer to display, on said control paneldisplay, data corresponding to said feedback signals.
 41. At least onestorage medium according to claim 36, wherein said computer-readabledata causes the single general purpose computer to store archival datacorresponding to said feedback signals.
 42. At least one storage mediumaccording to claim 36, wherein said computer-readable data causes thesingle general purpose computer to receive data from and/or transmitdata to at least one of a local area network and the internet.
 43. Atleast one storage medium according to claim 36, wherein saidcomputer-readable data causes the single general purpose computer toutilize fuzzy logic to control said plurality of injection moldingdevices.